1. Field of the Invention
The invention relates to chemically-amplified positive photoresist compositions that contain a resin that comprises acetal and alicyclic groups. Photoresists of the invention can exhibit notably enhanced lithographic properties. Preferred photoresists of the invention comprise one or more photoacid generator compounds and one or more phenolic resins that comprise a substituent that contains in covalent linkage one or more photoacid-labile acetal groups and one or more alicyclic groups such as adamantyl.
2. Background
Photoresists are photosensitive films for transfer of images to a substrate. They form negative or positive images. After coating a photoresist on a substrate, the coating is exposed through a patterned photomask to a source of activating energy such as ultraviolet light, EUV, e-beam, etc. to form a latent image in the photoresist coating. The photomask has areas opaque and transparent to activating radiation that define an image desired to be transferred to the underlying substrate. A relief image is provided by development of the latent image pattern in the resist coating. The use of photoresists is generally described, for example, by Deforest, Photoresist Materials and Processes, McGraw Hill Book Company, New York (1975), and by Moreau, Semiconductor Lithography, Principals, Practices and Materials, Plenum Press, New York (1988).
Chemically-amplified positive-acting photoresist compositions have involved cleavage of certain “blocking” groups pendant from a photoresist binder, or cleavage of certain groups that comprise a photoresist binder backbone, which cleavage a polar functional group is provided, e.g., carboxyl, phenol or imide, which results in different solubility characteristics in exposed and unexposed areas of the resist coating layer. See, for example, U.S. Pat. Nos. 5,075,199; 4,968,851; 4,883,740; 4,810,613; and 4,491,628, and Canadian Patent Application 2,001,384.
One approach to enhance photoresist lithographic performance of chemically-amplified positive photoresists has been to use one or more modified resin components. See, for instance, U.S. Pat. Nos. 6,042,997 and 6,492,086 and U.S. Patent Publications 20020012869, 20030232273 and 20040002017. See also U.S. Pat. No. 6,312,870 and U.S. Patent Publications 200301946643, 20030224289 and 20040034160; U.S. Pat. No. 6,312,870; Malik et al., Lithographic Properties of Novel Acetal-Derivatized Hydroxy Styrene Polymers, SPIE Proceedings, vol. 3678 pages 388-400 (1999); Uetani et al., Standard Developer Available ArF resist and Performance, SPIE Proceedings, vol. 3333 (pages 546-553; Fujimori et al., Structural design of a new class of acetal polymer or DUV resists, SPIE Proceedings, vol.3999, pages 579-590 (2000). See also T. Hojo et al., Journal of Photopolymer Science and Technology, 16(3):455-458 (2003).
While currently available photoresists are suitable for many applications, current resists also can exhibit significant shortcomings, particularly in high performance applications such as formation of highly resolved sub-quarter micron features.
For example, certain prior deblocking positive photoresists have contained resin components where a substantial mass of the resist resin undergoes a cleavage reaction which can cause significant shrinkage of the resist coating layer areas exposed to activating radiation. Such shrinkage can compromise resolution of the image patterned in the photoresist coating layer.
In addition to such undesired resist layer shrinkage, photoacid-induced of resist component(s) also can result in problems with outgassing of volatile cleavage reaction products. In particular, volatile photoacidolysis products can deposit on lens elements of exposure tools and degrade those tools, or require regular maintenance.
Prior photoresists also have exhibited deficiencies upon post-development processing of the substrate coated with the developed resist relief image. In particular, problems can arise upon etching a bared substrate surface defined by a developed resist relief image. For instance, to etch aluminum, silicon oxide and other substrates rather stringent conditions are often employed. Chlorine and fluorine-based gas etchants are frequently used and extensive localized heating often occurs during the etching sequence. As a consequence, the patterned photoresist coating on the substrate can experience shrinkage or other degradation. Such degradation can reduce resolution of the feature etched into the substrate and even render the substrate unusable for its intended purpose.
It thus would be desirable to have new photoresist compositions. It would be particularly desirable to have new photoresist compositions that could exhibit enhanced lithographic performance.